1. Field of the Invention
The present invention relates to a power supply device that includes a plurality of battery cells arranged side by side with separators being interposed between the battery cells, and a vehicle using the power supply device.
2. Description of the Related Art
A power supply device or a battery system has been developed that includes a number of battery cells arranged side by side, and forcedly blows cooling air to cooling gaps between the battery cells. This type of power supply device or battery system is used for vehicles such as hybrid car and electric vehicle. Since this type of power supply device employs a number of battery cells, the battery cells will have temperature difference among them. In particular, in the case where the number of the battery cells arranged side by side is large, it is difficult to cool all the battery cells to uniform temperatures, in other words, to temperatures that fall within a small range. It is very important for a vehicle battery system including a number of battery cells arranged side by side to reduce the temperature difference among battery cells as small as possible. The reason is that temperature difference may cause uneven remaining capacities of the battery cells, and as a result deteriorate the life of some battery cells. The efficiency of batteries in charging/discharging operation varies in accordance with their temperatures. For this reason, in the case where batteries have temperature difference, even if the batteries are charged/discharged at the same current, the batteries will have different remaining capacities. If the batteries have different remaining capacities, when a battery is likely to have a larger remaining capacity, the battery is likely to be overcharged. On the other hand, when another battery is likely to have a smaller remaining capacity, the battery is likely to be over-discharged. If a battery is overcharged or over-discharged, the battery will deteriorate faster. As a result, the life of the vehicle battery system will be reduced. In particular, in the case of the vehicle battery system for hybrid car, plug-in hybrid car, electric vehicle and the like, since a number of side-by-side arranged batteries are provided to be charged/discharged at a large amount of current, its manufacturing cost will be very expensive. For this reason, it is important for the vehicle battery system to increase its life. In particular, as the number of batteries used in the vehicle battery system increases, its manufacturing cost increases. Also, from this viewpoint, it is required to increase the life of the vehicle battery system. Contrary to this, as the number of side-by-side arranged batteries increases, temperature difference in the vehicle battery system will increase, which in turn may reduce the life of vehicle battery system.
A vehicle battery system has been developed that includes a plurality of battery cells arranged side by side, and forcedly blows cooling air to cooling space between the battery cells (Japanese Patent Laid-Open Publication 2007-250515).
In the vehicle battery system disclosed in Japanese Patent Laid-Open Publication 2007-250515, as shown in a cross-sectional view of FIG. 27, cooling gaps 103 are formed between battery cells 101 of battery block 110, and inlet and outlet ducts 106 and 107 are provided on the both sides of the battery block 110. The vehicle battery system forcedly blows cooling air through the inlet duct 106 to the cooling gap 103 so that the cooling air is discharged through the outlet duct 107. Thus, the battery cell 101 is cooled.
However, in the system in that the battery cells are cooled one after another by the cooling air, although a battery cell located closer to the inlet duct is cooled well by cold cooling air that just arrives at this battery cell, the cooling air is forcedly moved and is gradually heated by repeated heat exchange between the cooling air and battery cells. For this reason, there is a problem in that, when battery cells are arranged side by side in the longitudinal direction of a cooling duct, temperature difference will arise due to the positional difference among the battery cells. Such temperature difference among the battery cells may cause property deterioration of a battery cell and life difference among the battery cells. In particular, the output of the battery system is restricted by a battery cell having the lowest temperature. For this reason, in order to maximize the performance of the battery system, ideally, it is desired to bring ΔT (the difference between the highest and lowest battery temperatures) to zero.
In order to solve the aforementioned problem, the applicant has developed power supply devices shown in FIGS. 28 and 29. In the power supply device shown in FIG. 28, temperature equalizing plates 2815 are fastened to bind bars 2811 that couple battery cells 1 of a battery block 283 to each other. Also, in the power supply device shown in FIG. 29, temperature equalizing plates are formed integrally with bind bars 2911 that couple battery cells 1 of a battery block 293 to each other. The temperature equalizing plates are arranged on side surfaces of the battery block 283 or 293, and partially close the cooling gaps 284 or 294 between the battery cells 1. The opening area of the temperature equalizing plate is gradually changed so that the cooling gap 284 or 294 gets narrower particularly toward the upstream side into which cooling gas is blown. In the battery blocks 283 and 293, the amounts of blowing cooling gas are adjusted for battery cells one by one by the temperature equalizing plates so that the temperature difference among the battery cells 1 can be reduced.
However, in this construction, since the bind bar is constructed as the temperature equalizing plate, the bind bars will be required to have different shapes and sizes depending on the sizes of battery cells and the number of side-by-side arranged battery cells. Accordingly, bind bars will be necessarily redesigned specially for battery blocks. As a result, there is a problem that the cost will be increased.
In order to further solve this problem, the applicant has developed power supply devices shown in FIG. 30. In this power supply device, a temperature equalizing plate 3015 separate from the bind bar is attached onto a side surface of a battery block 303. The temperature equalizing plate 3015 is formed of plastic with flexibility, and is fastened to an end plate 310 on the battery block 303 end surface. The shape of the temperature equalizing plate 3015 is designed to restrict cooling effect on battery cells. The restriction amount gets larger as closer to a battery cell on the upstream side of cooling gas. The restriction is achieved by closing cooling gaps 304 with the temperature equalizing plate 3015. The closing amount gets smaller along the flowing direction of cooling gas. In this battery block 303, the temperature equalizing plate 3015 serves as a baffle so that the amount of blowing cooling gas is regulated. As a result, the temperature difference among the battery cells 1 can be reduced.
However, since the temperature equalizing plate is constantly blown with the forcedly blowing cooling gas, the blowing cooling gas causes a free end of the temperature equalizing plate to fluster. As a result, there is a problem that the temperature equalizing plate produces noise. In addition to aged deterioration of the temperature equalizing plate, such flustering movement may cause deterioration of the resin temperature equalizing plate in strength. Such deterioration may facilitate flustering movement. In particular, in the case where the power supply device is used as a vehicle power supply device, since the power supply device is subjected to vibrations, such deterioration will be accelerated. In addition, when the temperature equalizing plate flusters, the cooling gap may be insufficiently closed so that battery cells may be insufficiently uniformly cooled.
The present invention is devised to further solve the above problems. It is a main object of the present invention is to provide a power supply device that can reduce temperature difference among battery cells and can suppress noise production, and a vehicle including the power supply device.